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Not a logical statement. Keep in mind I never said they were all failures. There are certainly a greater-than-random number of successes out there from folk using those formulas -- and you appear to be one of those.

What I did say was that the process is not reliable -- that is, its use does not guarantee either correct diagnosis nor accurate prediction of actual response. Sometimes it appears to work. But sometimes it definitely doesn't.

If something is truly "proof", it will always be repeatable-- or we will understand why it doesn't. There are people that are not happy with certain instruments that have had the same treatment that worked in other cases.

Stanwood made a great contribution in getting people dealing with action geometry issues. However, the limitations are becoming more apparent as time goes along. We have further work to do to isolate all the variables that affect piano touch.

Not a logical statement. Keep in mind I never said they were all failures. There are certainly a greater-than-random number of successes out there from folk using those formulas -- and you appear to be one of those.

What I did say was that the process is not reliable -- that is, its use does not guarantee either correct diagnosis nor accurate prediction of actual response. Sometimes it appears to work. But sometimes it definitely doesn't.

If something is truly "proof", it will always be repeatable-- or we will understand why it doesn't. There are people that are not happy with certain instruments that have had the same treatment that worked in other cases.

Stanwood made a great contribution in getting people dealing with action geometry issues. However, the limitations are becoming more apparent as time goes along. We have further work to do to isolate all the variables that affect piano touch.

I'm not going to argue that you're wrong, but I do think it is important to remember that with the Stanwood TD, as with anything else in piano work, the end result is largely due to the skill of the technician performing the task, as well as the desires of the owner. I've played a lot of Stanwoodized pianos (in addition to my own) and they all feel different, and I feel like that the results are largely due to the goal of whoever was doing the work. Mine is kind of a "middle of the road" touch, but I've played some where you could practically blow on the keys to make them play, and I've played others that feel like mine. Now that the Fandrich-Rhodes thingy is out, that is definitely the service I will offer my clients.

The Stanwood process is a tool. It is a well thought out and accurate tool.

It is neither well thought out nor accurate: *It involves assumptions that are contrary to basic physics. *It substitutes precision for accuracy. *It fails reliably to predict actual touch experience. *It is based on static measurement of "what's happening when nothing is happening" rather than dynamic events that unfold as key and hammer actually move.

It provided an excellent application of the formula to determine weight-scale accuracy to friction in piano actions. But it is time for us to recognize the limitations of this procedure which served well to introduce many to action touch issues and move on to other more valid and effective approaches.

Stanwood recognized the importance of strike weight and action ratio in determining how heavy a piano action feels. However, as far as I've seen, he offers no analytical basis for his observation. That is certainly the case in his patent, in which he only describes static balance, or, as he calls it, his "equation of balance." He seems to claim some proprietary ownership of that equation, which is a bit absurd, because calculating the static and inertial forces in a lever system is simple physics and has been understood and applied for many, many centuries.

As it turns out, strike weight and action ratio are the primary determinants of an action's moment of inertia, which can easily be shown by some simple math. I have done this math and published the result on the internet for anyone to see. Fandrich-Rhodes seem to explicitly recognize the issue of moment of inertia, which they are calling the "inertial touch force," and claim to include software that can calculate it. Given the straightforward and well known method of calculation, I would have no a priori reason to doubt their claim. They further claim that "nothing has been written about how to identify, quantify, and correct inertia problems in the grand piano action," which seems to be a bit of a stretch. My published analysis dates back to 2007, and surely can't be the only one in existence.

The Stanwood process is a tool. It is a well thought out and accurate tool.

It is neither well thought out nor accurate: *It involves assumptions that are contrary to basic physics. *It substitutes precision for accuracy. *It fails reliably to predict actual touch experience. *It is based on static measurement of "what's happening when nothing is happening" rather than dynamic events that unfold as key and hammer actually move.

It provided an excellent application of the formula to determine weight-scale accuracy to friction in piano actions. But it is time for us to recognize the limitations of this procedure which served well to introduce many to action touch issues and move on to other more valid and effective approaches.

I will reiterate, it is a well thought out tool.

Unfortunately, many technicians place responsibility for failure on everything but their own experience.

Understanding what pianists need is a matter of considerable experience. More than most know or are willing to admit.

Stanwood's "tool" is not a substitute for that experience.

In my opinion, true client satisfaction comes best when "tools" are applied wholly and completely for the benefit of the client.

As a related example, we see failures at the clients expense when we say "such and such" replacement piano hammer is the BEST and ONLY one for you.

The reality is, that hammer is the one the technician has the most experience with or benefits from selling. Neither of these treats the client unbiasedly and only benefits the client serendipitously.

Stanwood's work has suffered the inexperience of a great many folks using it.

Truth is, in the right hands, any tool has value. In the wrong hands, no tool has value.

Edited by Larry Buck (09/05/1209:39 AM)

_________________________"If I have seen further than others, it is by standing upon the shoulders of giants."Isaac Newton

*snip*As it turns out, strike weight and action ratio are the primary determinants of an action's moment of inertia, which can easily be shown by some simple math. .

Greetings, What am I missing? I have always kept the key weight (FW) as a prime component of the inertia a pianist deals with. Those leads move before anything else in the action.

SW and action ratio combine to define the resistance the key must propel, however, the research (Anders-Askenfeldt) shows that the key is often on the punching before the hammer has finished accelerating. My logic is that the mass of the key determines the first resistance the pianist feels, and that resistance increases rapidly, (geometrically? exponentially? logarithmically? somebody help me out here..) as the force applied increases. A heavy key gets hard to play at high speed, regardless of what is sitting on the back of it. Or, was something else intended by the post? Regards,

*snip*As it turns out, strike weight and action ratio are the primary determinants of an action's moment of inertia, which can easily be shown by some simple math. .

Greetings, What am I missing? I have always kept the key weight (FW) as a prime component of the inertia a pianist deals with. Those leads move before anything else in the action.

SW and action ratio combine to define the resistance the key must propel, however, the research (Anders-Askenfeldt) shows that the key is often on the punching before the hammer has finished accelerating. My logic is that the mass of the key determines the first resistance the pianist feels, and that resistance increases rapidly, (geometrically? exponentially? logarithmically? somebody help me out here..) as the force applied increases. A heavy key gets hard to play at high speed, regardless of what is sitting on the back of it. Or, was something else intended by the post? Regards,

According to Fandrich and Rhodes' research, strike weight is the overwhelming source of inertia: measurements from note A49 on a Steinway B revealed that the hammer was responsible for 81.8%, followed by the key (10.1%), lead weights (5.6%), and wippen (2.3%). Removing .6g of mass from this hammer reduced the overall inertia by 7% and a 4mm capstan moved reduced inertia by 14%. Altering the lead weights produced a nominal effect, except for removing them altogether and installing a strong turbo spring, which reduced inertia by 6%.

They're also supposed to be doing a multi-series article on their research in the Journal, hopefully starting this month, which should answer many of our questions.

*snip*As it turns out, strike weight and action ratio are the primary determinants of an action's moment of inertia, which can easily be shown by some simple math. .

Greetings, What am I missing? I have always kept the key weight (FW) as a prime component of the inertia a pianist deals with. Those leads move before anything else in the action.

SW and action ratio combine to define the resistance the key must propel, however, the research (Anders-Askenfeldt) shows that the key is often on the punching before the hammer has finished accelerating. My logic is that the mass of the key determines the first resistance the pianist feels, and that resistance increases rapidly, (geometrically? exponentially? logarithmically? somebody help me out here..) as the force applied increases. A heavy key gets hard to play at high speed, regardless of what is sitting on the back of it. Or, was something else intended by the post? Regards,

Sorry, but it's not the key weight that dominates. As felt by the pianist, the moment of inertia of the hammer and its shank gets multiplied by the square of the action ratio. Let's take a typical action ratio of 5.7. In that case, the hammer's moment of inertia, as felt by the pianist, would be multiplied by 32.5 times.

I think people often assume key weights are the problem because lots of key weights are required when hammers are heavy and/or the action ratio is high. You might say key weights are an indicator of the problem rather than the problem itself. You can read my derivation here . If you can find a mistake in my math, I'll be happy to change my mind.

*snip*As it turns out, strike weight and action ratio are the primary determinants of an action's moment of inertia, which can easily be shown by some simple math. .

Greetings, What am I missing? I have always kept the key weight (FW) as a prime component of the inertia a pianist deals with. Those leads move before anything else in the action.

SW and action ratio combine to define the resistance the key must propel, however, the research (Anders-Askenfeldt) shows that the key is often on the punching before the hammer has finished accelerating. My logic is that the mass of the key determines the first resistance the pianist feels, and that resistance increases rapidly, (geometrically? exponentially? logarithmically? somebody help me out here..) as the force applied increases. A heavy key gets hard to play at high speed, regardless of what is sitting on the back of it. Or, was something else intended by the post? Regards,

According to Fandrich and Rhodes' research, strike weight is the overwhelming source of inertia: measurements from note A49 on a Steinway B revealed that the hammer was responsible for 81.8%, followed by the key (10.1%), lead weights (5.6%), and wippen (2.3%). Removing .6g of mass from this hammer reduced the overall inertia by 7% and a 4mm capstan moved reduced inertia by 14%. Altering the lead weights produced a nominal effect, except for removing them altogether and installing a strong turbo spring, which reduced inertia by 6%.

They're also supposed to be doing a multi-series article on their research in the Journal, hopefully starting this month, which should answer many of our questions.

My own work, which I referenced above in my response to Ed Foote, showed that at middle C in the particular Steinway B that I analyzed, that hammer inertia was 83% of the total, the key and its lead weights was 14% of the total, and the wippen was 1.5% of the total. In general, my measurements and calculations correlate very well with those of Fandrich and Rhodes.

According to Fandrich and Rhodes' research, strike weight is the overwhelming source of inertia: measurements from note A49 on a Steinway B revealed that the hammer was responsible for 81.8%, followed by the key (10.1%), lead weights (5.6%), and wippen (2.3%). Removing .6g of mass from this hammer reduced the overall inertia by 7% and a 4mm capstan moved reduced inertia by 14%. Altering the lead weights produced a nominal effect, except for removing them altogether and installing a strong turbo spring, which reduced inertia by 6%.

Interesting, however, I have to question the completeness of information. Is strike weight the overwhelming source of inertia at all levels of play? I think as the speed of movement increases the mass of the key becomes more influential, so at what speed does Fandrich and Rhodes' research make the claim? Any speed, or something specifically slower that full blast? Regards,

As the Five Lectures info describes it, the key is moving well before the hammer, so inertial levels of the hammer may as well be infinite in relation to accelerating the key.

According to Fandrich and Rhodes' research, strike weight is the overwhelming source of inertia: measurements from note A49 on a Steinway B revealed that the hammer was responsible for 81.8%, followed by the key (10.1%), lead weights (5.6%), and wippen (2.3%). Removing .6g of mass from this hammer reduced the overall inertia by 7% and a 4mm capstan moved reduced inertia by 14%. Altering the lead weights produced a nominal effect, except for removing them altogether and installing a strong turbo spring, which reduced inertia by 6%.

Interesting, however, I have to question the completeness of information. Is strike weight the overwhelming source of inertia at all levels of play? I think as the speed of movement increases the mass of the key becomes more influential, so at what speed does Fandrich and Rhodes' research make the claim? Any speed, or something specifically slower that full blast? … As the Five Lectures info describes it, the key is moving well before the hammer, so inertial levels of the hammer may as well be infinite in relation to accelerating the key.

There are a couple of things at work here. Roy is quite right in his analysis of the effect of the different components of the piano action; hammers are, by far, the biggest contributor to the overall inertia of the action. As Roy also points out, key leads are an indicator of an inertia problem; they are not all that much of the problem in and of themselves.

The article by Anders Askenfelt & Erik Jansson, ”From Touch to String Vibration,” tells only a small part of the story when it comes to explaining how the piano action works. In all piano actions there is a time delay between the initial key strike and the motion of the hammer. How much of a delay between the key strike and the motion of the hammer—and then the actual acceleration curve of the hammer—depends on many factors including the length, shape and stiffness of the key, the compliance of the many felt and leather components in the action, the stiffness of the various wood action components and, most significantly, the mass of the hammer itself. None of these are constants.

When a key is struck very lightly the lag between key motion and hammer motion is relatively small. That is, there is little key bending, little compression—beyond the static compression—of the felt and leather parts and little bending in the wippen levers and the hammershank. The motion of the hammer tracks the motion of the key fairly accurately.

When the key is struck with a very hard blow the lag between the motion of the key and the resultant hammer motion is significant. Indeed, in all piano actions there will be a point at which a harder key strike will no longer result in any additional hammer velocity. This is the point at which the key actually strikes bottom before the hammer starts to move. This is called the point of ”action saturation.”

The point of action saturation is different in every action and, indeed, from key to key within a given action. Action saturation will be reached sooner with keys having a significant dogleg than in keys that are relatively straight. It will be reached sooner in an action using thick, soft balance rail punchings. Sooner in an action—like the concert grand action I looked at last week—using relatively soft felt under the knuckle leather. Sooner in an action using heavy hammers. Etc.

All other things being equal, action saturation will occur sooner in an action using heavier hammers than in an action using lighter hammers. This, because the inertia of the hammer is so great that it takes more force to accelerate it and the action components are only capable of transferring so much energy from the keys to the hammers. Beyond this they simply twist, bend and compress.

Generally in these discussions we tend to think of the energy transfer from the key front to the hammer as 100% efficient and instantaneous; it is not. How energy is stored and released within the various action components is greatly affected by hammer mass. A relatively compliant action that works very nicely with light hammers will be quickly saturated with heavy hammers. In this case the quality of touch and/or feel has nothing to do with how well the action is going to function; it is going to be overwhelmed fairly early on no matter how many leads there are or are not in the keys.

Generally in these discussions we tend to think of the energy transfer from the key front to the hammer as 100% efficient and instantaneous; it is not. How energy is stored and released within the various action components is greatly affected by hammer mass. A relatively compliant action that works very nicely with light hammers will be quickly saturated with heavy hammers. In this case the quality of touch and/or feel has nothing to do with how well the action is going to function; it is going to be overwhelmed fairly early on no matter how many leads there are or are not in the keys.

ddf

ABsolutely very well stated Del .

_________________________
Professional of the profession.

I wish to add some kind and sensitive phrase but nothing comes to mind.!

Del, Your getting into explaining why harder is not louder. When the enthusiastic teenager starts breaking strings, I tell them to view the piano like a drum head. Any knucklehead can put a stick right through the drum head. It takes a skilled musician to make it sound like a gun shot.

Mostly, so far the discussion is, at least as I read it, concerned with the "effort" part of the stroke, which I interpret to mean the part of the stroke which ends at the key bottoming on the punching.

From the the pianist's perspective, especially in rapid play,the kickback imparted by the parts already in motion, which have a mind of their own at this point, is a significant factor in what an action feels like in play...at least that's my take.

Although the SW has been mentioned as the determining source of inertia, a concept that is kind of "duh" science, in play, the returning key, with shank in free motion and then the reversing of that weighted key's direction impart significant information that determines how a pianist reads the action in play.

The SW/ratio/friction determines how much lead is going into the key, but once the lead is in the key, the key's momentum and/or inertia (if these are not the same things...physicists?)becomes a significant factor in determining the dynamic touch....No?

Not so much, probably the "free key" behavior have its importance on touch, but even somewhat large difference in leading can remain discrete. Yesterday I worked on a piano (Steinway O) from 1908

in the high basses a white key have zero lead, while the neighbors (white too) have 3 leads. [edit : I am sorry I only looked on one side, possible half leads are used...]

One would expect the difference in touch to be fairly noticeable, it is not, at last in most basics mode of play.

I will be there today, and I will check against fast staccato play, and slow forceful, so to say, other modes, and I let you know the differences I can perceive.

There are no assist springs on that Steinway (from the start visibly) the action is light but with a good balanced feel.

When I talk of the rebound it is more or less anecdotal, but a key without lead on an action with assist spring will have little inertia, possibly not enough to be at ease in some modes of play (but it can be also appreciated by some pianists, as I have been told yet, to my surprise, just feeling a "transparent key") .If the assist springs where not prejudicial to the upward motion of key/action I would have used them more often.

I understand now that even if they lower/suppress the whippen inertia, this last have not a really noticeable inertia.

What count more in action is probably the quality of acceleration progression between levers. indeed assuming the hammer SW is well related to the action ratios.

(changing from 4.5:1 to 5.5:1 between rest and let off moment, for instance...)

(dont know if is a good ratio "evolving" but this is what can be find in a short grand action, for instance.

Edited by Kamin (09/06/1205:34 AM)

_________________________
Professional of the profession.

I wish to add some kind and sensitive phrase but nothing comes to mind.!

*snip*As it turns out, strike weight and action ratio are the primary determinants of an action's moment of inertia, which can easily be shown by some simple math. .

Greetings, What am I missing? I have always kept the key weight (FW) as a prime component of the inertia a pianist deals with. Those leads move before anything else in the action.

SW and action ratio combine to define the resistance the key must propel, however, the research (Anders-Askenfeldt) shows that the key is often on the punching before the hammer has finished accelerating. My logic is that the mass of the key determines the first resistance the pianist feels, and that resistance increases rapidly, (geometrically? exponentially? logarithmically? somebody help me out here..) as the force applied increases. A heavy key gets hard to play at high speed, regardless of what is sitting on the back of it. Or, was something else intended by the post? Regards,

Sorry, but it's not the key weight that dominates. As felt by the pianist, the moment of inertia of the hammer and its shank gets multiplied by the square of the action ratio. Let's take a typical action ratio of 5.7. In that case, the hammer's moment of inertia, as felt by the pianist, would be multiplied by 32.5 times.

I think people often assume key weights are the problem because lots of key weights are required when hammers are heavy and/or the action ratio is high. You might say key weights are an indicator of the problem rather than the problem itself. You can read my derivation here . If you can find a mistake in my math, I'll be happy to change my mind.

This is a very well produced document, I like the analysis (did not go thru the numbers of course but the reasoning is easy to follow)

Thanks for providing the result of your work, it is so interesting.

To me what make action feel is the good relations between the leverage progression , we expect the hammer gravity center to move in a predictable way at each note same, that is what gives control on the acceleration, with a very tiny moment at the end of the stroke where the breaking induced by the jack friction during let off, allow to correct or manipulate a little more the acceleration in some modes of playing.

the way the hand take control on the acceleration is all but a "yes or no" thing.

the pianists hand mass is managed with its own inertia so to match the action inertia, but then muscles manage acceleration.

_________________________
Professional of the profession.

I wish to add some kind and sensitive phrase but nothing comes to mind.!

Mostly, so far the discussion is, at least as I read it, concerned with the "effort" part of the stroke, which I interpret to mean the part of the stroke which ends at the key bottoming on the punching.

From the the pianist's perspective, especially in rapid play,the kickback imparted by the parts already in motion, which have a mind of their own at this point, is a significant factor in what an action feels like in play...at least that's my take.

Although the SW has been mentioned as the determining source of inertia, a concept that is kind of "duh" science, in play, the returning key, with shank in free motion and then the reversing of that weighted key's direction impart significant information that determines how a pianist reads the action in play.

The SW/ratio/friction determines how much lead is going into the key, but once the lead is in the key, the key's momentum and/or inertia (if these are not the same things...physicists?)becomes a significant factor in determining the dynamic touch....No?

Jim Ialeggio

I'm not so sure that kickback or rebound, as you called it, is much of a factor in the action feel as the key and other action components return to their rest positions. The hammer does bounce off the string with some energy--energy which, of course, depends on how hard the hammer strikes the strings. However, most of that energy is lost during check; the hammer tail scrubs against the backcheck, turning the hammer's rebound energy into heat. What's left is only the energy stored in the balancier's spring. I suppose the motion of the hammer as it leaves check is somewhat felt in the key, but I'm not so sure that it is significant.

Once again, however, we find that hammer mass and action ratio are significant, as they greatly affect the time it times for the action parts to reset. Forgetting any effects of hammer and felt rebound for the moment, the only force trying to reset the action is the up weight. This force has to accelerate the action components. Think back to Newton's famous formula f = ma, or in the world of rotating components, T = Ia, where T is torque, I is moment of inertia, and a is angular acceleration. We see that the acceleration of the action as it resets is inversely proportional to moment of inertia. We can go further and solve for the time it takes to reset, and find that t = sqrt(2*alpha*I/T), where alpha is the angular travel of the key.

BTW, your description of the hammer mass as dominating the moment of the inertia as duh science seems a bit gratuitous. Like lots of things, it's only after someone makes the effort to do the numbers that it seems obvious. It's also obvious that many, if not most, people in the piano community are not aware of this fact.

<snip> Forgetting any effects of hammer and felt rebound for the moment, the only force trying to reset the action is the up weight. This force has to accelerate the action components.

Um, the spring, compressed and held at check is a major player in the reset speed of the action. It accelerates the key, and since upweight is usually measured with the spring out of the equation, I don't think we can ascribe exclusive force of resetting to upweight, alone.

<snip> Forgetting any effects of hammer and felt rebound for the moment, the only force trying to reset the action is the up weight. This force has to accelerate the action components.

Um, the spring, compressed and held at check is a major player in the reset speed of the action. It accelerates the key, and since upweight is usually measured with the spring out of the equation, I don't think we can ascribe exclusive force of resetting to upweight, alone.

Well, I'm not so sure about that. As long as the hammer is held in check, the spring exerts no force. As the hammer starts to leave check, some of the spring's energy is dissipated as friction between the hammer tail and the back check. Finally, any spring energy that's left can supply force only as long as the hammer is accelerated upward or there is contact between the end of the balancier and and the drop screw. But, we must take into account the fact that friction at the balancier action center, which is usually pinned quite tightly, absorbs more of the spring's energy.

I thinks it's obvious that there's enough complexity here to require measurement and analysis before a firm conclusion can be reached.

[ As long as the hammer is held in check, the spring exerts no force. As the hammer starts to leave check, some of the spring's energy is dissipated as friction between the hammer tail and the back check. Finally, any spring energy that's left can supply force only as long as the hammer is accelerated upward or there is contact between the end of the balancier and and the drop screw. .

I have to disagree. As long as the hammer is held in check, the spring is exerting its maximum force. It is potential, not kinetic. It is this force, acting against the checked hammer,via the rep/knuckle contact that is mainly responsible for the key's upward speed. When the key is released, in fast repetition, the hammer remains motionless, acting as the inertial resistance to the spring, which dumps all of its potential,(minus friction), into moving the key upwards. It is still motionless when the jack resets, (at least, according to the high-speed films I have seen of fast repetition).

I repeat: under even moderately fast repetition, the hammer only moves upward when the jack returns and sends it up. You can observe this by playing a hammer into check, and then sliding you finger off the front of the key, allowing it to rise unimpeded. You will see the hammer drop, not rise. And it may be a quibble, but the drop screw is only in contact with the repetition lever between the beginning of let-off and the hammer's first 1/16" or so rebound from the string and has little effect on repetition, ( unless it allows the hammer to be struck by the vibrating string and impels it below check,causing catastrophic repetition failure.)Regards,

[ As long as the hammer is held in check, the spring exerts no force. As the hammer starts to leave check, some of the spring's energy is dissipated as friction between the hammer tail and the back check. Finally, any spring energy that's left can supply force only as long as the hammer is accelerated upward or there is contact between the end of the balancier and and the drop screw. .

I have to disagree. As long as the hammer is held in check, the spring is exerting its maximum force. It is potential, not kinetic. It is this force, acting against the checked hammer,via the rep/knuckle contact that is mainly responsible for the key's upward speed. When the key is released, in fast repetition, the hammer remains motionless, acting as the inertial resistance to the spring, which dumps all of its potential,(minus friction), into moving the key upwards. It is still motionless when the jack resets, (at least, according to the high-speed films I have seen of fast repetition).

I repeat: under even moderately fast repetition, the hammer only moves upward when the jack returns and sends it up. You can observe this by playing a hammer into check, and then sliding you finger off the front of the key, allowing it to rise unimpeded. You will see the hammer drop, not rise. And it may be a quibble, but the drop screw is only in contact with the repetition lever between the beginning of let-off and the hammer's first 1/16" or so rebound from the string and has little effect on repetition, ( unless it allows the hammer to be struck by the vibrating string and impels it below check,causing catastrophic repetition failure.)Regards,

Consider the hammer held in check. The rep spring is trying to move the hammer upward by pushing on the knuckle. The hammer, while in check, is effectively connected to the back of the key. So, while in check, the rep spring is trying to hold the back of the key up. Therefore, in this condition, the rep spring is at least partially inhibiting the back of the key from falling, or at least not adding any force at all to the reset process. It is only after the hammer leaves check that the rep spring can help in action reset. When one subtracts out friction and considering the fact that the force of the rep spring is only applied for a portion of the key travel, I'm just not sure how significant it's force is. As I said before, I believe some measurements and analysis needs to be done before any firm conclusions can be reached.

Consider the hammer held in check. The rep spring is trying to move the hammer upward by pushing on the knuckle. The hammer, while in check, is effectively connected to the back of the key. So, while in check, the rep spring is trying to hold the back of the key up. Therefore, in this condition, the rep spring is at least partially inhibiting the back of the key from falling, or at least not adding any force at all to the reset process. It is only after the hammer leaves check that the rep spring can help in action reset. When one subtracts out friction and considering the fact that the force of the rep spring is only applied for a portion of the key travel, I'm just not sure how significant it's force is.

I am real sure how significant it is, having dealt with hundreds of actions that were not repeating very well.

I think the difference here is one of perspective:

Consider the hammer in check. The rep spring is trying to move the key back up by pushing against the whippen. And it will begin to do this the instant it is released from check. It is only after the check leaves the hammer that the key rises and the spring moves the key rather than the hammer. It is significant because the spring accelerates things faster than gravity alone, and added acceleration at the very beginning of the return is most valuable. I haven't found that strengthening the spring to excessive levels speeds up the action nearly as much as the checking height. It just makes escapement a ruder interruption than it needs to be at ppp levels of play. This is a waste of sensitivity, since inre repetition speed, is not usually important whether the spring causes as rapid a hammer rise as possible without feeling it or whether it creates a detectable recoil as it throw the knuckle off the jack, repetition will be the same.

I am building fast actions with gentle springs, tight balancier pinning, and 5/8" checking heights. A pianist that requires faster repetition and doesn't need a lot of power in them can usually be satisfied by raising the check height to 3/8", or less if you can get it. There is less power in a stroke that short, but it allows the key to reset without so much upward travel. It can make up for poor technique, I am told.

I could test on that Steinway O, in the end there are 2 white keys without any lead, at a fourth interval.

All other keys around them have 3 leads (I made some pics.

The main difference lies in the tone, which is stronger with the lead.

It is also harder to play fast the leaded keys the non leaded ones are easier, the 3 leads can be felt as braking the keys when one want to play rapidly. seem to slow the rise of the key as the lowering.

Out of that, even knowing the fact, differences are not easy to feel in the fingers at slower speeds.

The tone, yes, the touch, not really...

Edited by Kamin (09/06/1206:44 PM)

_________________________
Professional of the profession.

I wish to add some kind and sensitive phrase but nothing comes to mind.!

I did some experiments using an action model. As usual, I found out something that was unexpected.

Test 1 I pressed the key down until just before the start of letoff and before the balancier was displaced by the drop screw. I held the key in this position and then measured the amount weight it took to just start the key in its upward move. This amount of weight was less than what is normally considered the up weight.

Test 2I slowly lowered the key to the bottom of the stroke. Because of the slowness, the hammer was not in check. I once again measured the amount of weight that it took to just start to raise the key. It was about 5 grams higher than in the first test.

Test 3I fully depressed the key and manually put the hammer into check. In this case, the weight required to just get the key moving was the same as in case 2. The reason for this is that the hammer was released from check very rapidly.

ResultFor the particular key I tested, the compression of the balancier spring provided about 5 extra grams of up force, but only over a very short distance, because the hammer resets quite quickly, using only a small portion of the key stroke.

Unexpected resultI found that the compression of the front-rail felt provided lots more rebound force than the balancier spring. This effect is hard to quantify because the force provided depends on how hard the key is pressed, and how quickly it is released. I would make the tentative conclusion that the felt compression can be a significant factor in how quickly the key resets. If this is true, it would suggest that soft front-rail felts would be more effective than stiff felts, because the soft felts, by compressing more, store more energy. This result is quite interesting as it suggests that front-rail felt could be fabricated and selected based on this criterion as well as its contribution to action feel.

Once again, a quick experiment has potentially revealed information that is poorly understood in the piano community. Experiments beat jaw flapping by a mile any day (and I'm not excepting myself).

Larry Fine, in his Fall 2012 Piano Buyer's Guide (which I read on the web) lists the Stanwood Touch Design under "problem solving".

One of the reasons that my technician was not so keen on this is that (in his words ) it can be used to mask problems with an action. When I mentioned that a piano with Stanwood touch design played very well, his response was - "yes, but for how long?" Is this a valid comment? And if so, would a technician that I bring to inspect a potential purchase be able to opine on whether the Stanwood method applied to the piano I am considering is masking a problem or is in fact an enhancement to an acceptable action?